Apparatus and method for data copy consistency in a multi-cache data processing unit

摘要

In a multi-processor unit data processing system, apparatus and method are described for providing that only the most recent version of any data signal group will be available for manipulation by a requesting data processing unit. A "multiple" state for a data signal group is defined by the presence of a particular data signal group stored in the cache memory units of a plurality of data processing units. The "multiple" state is associated with each copy of a data signal group by control signals. When a data signal group is changed by the local data processing unit, an "altered" state is associated with the new data signal group. The simultaneous presence of an "altered" state and "multiple" state is forbidden and requires immediate response by the data processing system to insure consistency among the data signal groups. In addition to apparatus for identifying and storing the state of the data signal groups, apparatus must be provided for communication of the selected states to the data processing units.